1. Field of the Invention
This invention relates generally to carpenter's levels, and more particularly to a vial mounting system for such a level, the system enabling the level to compensate for temperature changes over a wide ambient temperature range.
2. Description of Related Art
The following art defines the present state of this field:
Lemile, U.S. Pat. No. 676,330 describes improvements in the construction of spirit-levels, more especially the manner of mounting the level or glass or vial, and to enable the latter to be readily adjusted vertically from the exterior and to cushion the same.
James, U.S. Pat. No. 778,130 describes improvements in spirit levels, and the object is to provide an improved construction of spirit-level having simple and effective means for attaching the liquid-tube to the support and conveniently adjusting the same.
McCain, U.S. Pat. No. 808,862 relates to leveling and plumbing instruments, and it consists of a chambered bar provided with a pivoted spirit-level and a shaft and cam for adjusting the same to an extent indicated by a pointer on the shaft.
Oswald, U.S. Pat. No. 935,807 describes an improvement in the construction of spirit level attachments, and to provide a simple, inexpensive and efficient device of this character capable of ready adjustment to arrange the bubble tubes in proper position with relation to the instrument, and adapted to permit a bubble tube to be readily removed and replaced by a new tube, should the bubble tube be broken or otherwise impaired through rough handling of the instrument.
Lofberg, U.S. Pat. No. 1,012,668 describes improvements in levels and has for its object the provision of an improved level of simple construction and efficient operation.
Ellison, U.S. Pat. No. 1,298,024 describes a spirit level which may be easily and readily applied to or detached from a level-stock, so that bricklayers, masons, or other artisans who use such leveling instruments may carry the spirit level to and from their work and apply the same to any suitable level-stock.
Hubbard, U.S. Pat. No. 2,487,245 relates to a level of the type used by carpenters, bricklayers, and other workmen erecting buildings and other structures which must be kept perpendicularly and horizontally accurate. If such levels are not carefully handled the casings or rings holding bubble glasses are liable to move out of their proper positions and the level will not be accurate.
Scheyer, U.S. Pat. No. 4,774,767 describes a water level or spirit level having at least one water level member whose angular adjustment relative to the contact surface can be changed. The water level member is rotatably mounted on the level body or a structural part fixedly connected to the level body. The water level member is fixable in the desired angular position relative to the level body or the structural parts connected to the level body. The rotatable water level member has at least one circumferentially extending flange which engages under a clamping jaw. The clamping jaw can be pressed against the surface of the flange by means of a manually operated clamping member.
Dengler, U.S. Pat. No. 4,860,459 describes a bubble level with a hollow metal section that has a circular window, in which a cylindrical level tube for a vertical level can be inserted with a positive interlock in the axial direction and can be fastened with a material interlock. A level support is inserted into the hollow section in the axial direction. The support has a cylindrical seat aligned with the window, to receive a level holder that bears a level. An interlock device is disposed between the level support and the level holder. By means of this interlock device, the level holder is mounted axially fixed, but rotatable until it is fastened by the material interlock.
Bird et al, U.S. Pat. No. 4,999,921 describes an adjustable spirit level having a plurality of spirit levels therein. A first spirit level measures vertical orientation, a second adjustable spirit level is adjustable to a true horizontal position, and a third spirit level is adjustable to any desired position between vertical and horizontal. The second level may be adjusted with a rotatable cam-shaped end piece secured within the level body, while the third level is ratcheted to a predetermined angle. The third level may be held in place by a spring member biasing the level against the level body.
Tate, U.S. Pat. No. 5,111,589 describes an adjustable plumb level formed from an I beam with wood side panels. A circular hole is formed through the I beam and side panels, within which an indicating mechanism is disposed. The indicating mechanism is easily replaceable so that the present invention can be used as a plumb or a level.
Tate, U.S. Pat. No. 5,177,873 describes an adjustable plumb level having a first gear driven by a second gear. The second gear has a smaller external diameter than does said first gear. The second gear is operatively coupled to first gear so that when an external force causes the second gear to rotate, the first gear also rotates. The first gear includes a straight vial disposed in the center thereof.
The prior art teaches the use of an adjustable vial and of a means for adjustment of the vial position in order to calibrate the leveling device. However, the use of a linear expansion joint is not taught and such ajoint enablement in combination with an excentric pivot mount is novel in the art. There is a need for a general purpose leveling tool that is able to sustain the physical shocks encountered in normal use as well as the occasional severe shocks encountered under unusual circumstances such as when the tool is dropped. There is a need for a leveling tool that is able to be easily and quickly calibrated as required. There is need for a leveling tool that is able to self adjust for thermal expansion and contraction due to its use in severe environments. The present invention fulfills these needs and provides further related advantages.